1. Field of the Invention
The present invention relates to a method for replacing a utility pole without cutting off the power supply, that is, removing an existing utility pole and erecting a new utility pole during maintenance and repair of the overhead electrical distribution line. More particularly, the utility pole replacement work is performed as follows: a pole clamp mounted on an auger crane grasps the upper portion of the old utility pole; a separate pole crusher cuts the concrete of the old utility pole; the lower portion of the old utility pole is removed and a new utility pole is installed; the arm and wire of the old utility pole are transferred to the new pole without cutting off the power supply thereby saving work, because a temporary interruption of electrical power is not required.
2. Description of the Related Prior Art
During maintenance and repair of overhead power distribution lines, it is frequently required to replace a utility pole due to a vehicle collision or general deterioration. In such a case, the work is done by erecting a new utility pole near the utility pole to be removed, and the arm and wire from the utility pole to be removed are relocated to the new utility pole using a wire relocation apparatus, without interrupting the supply of electricity.
Namely, if an accident occurred when a car, for example, collided with a concrete utility pole, the impacted portion would be damaged or the utility pole itself would be broken. And if the service life of the concrete material is exceeded, it quickly deteriorates, so it should be replaced with a new utility pole periodically.
And in the case that a new utility pole cannot be erected near the utility pole to be removed, the new utility pole should be erected in the same place as the utility pole to be removed. In such a case, because it is impossible to perform the work using the aforementioned wire relocation apparatus, the work is done using an auxiliary support device of a temporary transmission method using a bypass cable, which also allows uninterrupted flow of power during the repair.
In the case of replacing utility poles without service interruption, if a new utility pole can be erected near the utility pole to be removed, it is possible to do so using a wire relocation apparatus. But if the new utility pole should be erected in the same place where the utility pole to be removed already stands, the wire relocation apparatus cannot be applied. In such a case an auxiliary support device can be applied to replace the utility pole without interrupting service, but it is uneconomical and inefficient because the live wire is temporarily moved to an auxiliary support device made of an insulated auxiliary arm attached to an auger crane, and the wire must then be moved again to the new utility pole after the utility pole is replaced. Besides that, there is another problem in applying this method since it has a limitation of being applied only to a straight utility pole—it is impossible for utility poles of other shapes to cope with the case that the allowable tensile load of the auxiliary support device is exceeded.
Due to such a problem it is inevitable to perform the work by applying the temporary transmission method using a bypass cable. But it involves many problems such as requiring high construction cost, obstructing traffic due to equipment occupying the road, and risking the safety of pedestrians and workers.
In addition, in uninterrupted replacement work of utility poles as mentioned above, there is an inevitable case that a new utility pole has to be erected in the same place where the utility pole to be removed was erected due to the circumstances of the site where work is being done. In such a case, the auxiliary support device or the temporary transmission method using a bypass cable is traditionally applied. But the method using the auxiliary support device has a problem when the ground is not level and can be applied only to a straight utility pole, since it exceeds an allowable tensile load of the auxiliary support device, and the temporary transmission method using a bypass cable also has many problems as mentioned above. Finally, both above-mentioned methods cannot be applied to the case where commonly installed communication equipments cannot be relocated on the same day.
Namely, the uninterrupted replacement work, which is the most general form of replacing utility poles, includes a series of work processes such as the process of relocating the arm and wire from the old utility pole to the new utility pole without interrupting electrical service using a wire relocation apparatus after the new utility pole is erected on one side of the utility pole to be replaced, and the process of completing the work by removing from the ground the old utility pole after the relocation of the arm or wire is completed.
But if a building or structure is erected around the existing utility pole, or if it is difficult to excavate the ground or surface, it may be impossible to secure space for erecting a new utility pole.
Conventionally, if it is impossible to secure sufficient space for erecting a new utility pole, work is carried out by applying the method using an auxiliary support device or the method using a bypass cable although they have problems as mentioned above. Moreover, because both methods cannot be applied in a case where it is impossible to relocate commonly installed communication equipment on the same day, the deteriorated utility pole is not replaced and is left in service despite the fact that the replacement time has passed due to deterioration of the utility pole. Consequently, the utility pole is exposed to risks such as damage or destruction by natural disasters including typhoons, etc.